Turfgrass IPM Advisory

Seasonal Turfgrass Pest Update, Utah State University Extension, Winter 2016

Turfgrass Management At this time of year, your thoughts may be turning to the potential effects of winter

conditions on your turf. “Winterkill” is the general term describing turf August loss 28, that 2008 Volumemay VII occur as a result of winter conditions. This issue will discuss the actual causes of winterkill and how they may be prevented. News/What to Watch For During winter, most turfgrass diseases and insects are relatively inactive. However, one disease complex, the snow molds, may be at work despite current low temperatures.

Focus on: Winterkill

When turfgrasses die over the winter months, Dessication it may generally be described as “winterkill” (Figs. 1 and 2). The term covers During the winter when turfgrass plants are a multitude of actual causes of turfgrass dormant or semi-dormant, drying of the death in the winter, which may include snow leaves or plants (dessication) may cause mold, low temperatures, ice sheets, death. Dessication is typically only a factor dessication and crown hydration. on elevated or extremely exposed or windy sites, and areas where surface runoff is rapid. Crown Hydration

Crown hydration is of most concern during the warmer days of late winter or early spring when there is the potential for a day or two of warm daytime temperatures followed by a hard freeze. Turfgrass plants may start to take up water as temperatures warm and then re-freeze rapidly. As a result, ice crystals may form in the crown of the plant, rupturing cells and causing death.

Of the commonly-used cool-season turfgrass species, annual bluegrass and creeping bentgrass are most susceptible to crown hydration problems, though annual bluegrass Figure 1. Winterkill symptoms in turfgrass. is the more susceptible of the two because it emerges from dormancy earlier. Low-Temperature Kill

Different turfgrass species are naturally more or less hardy in cold temperatures. In addition, the rates of freezing and thawing, the number of times frozen, and post-thawing treatment of the turf also affect low- temperature injury to grasses. Of greater concern than air temperature for low- temperature kill of turf is soil temperature, since the crowns of the plants reside within the soil. Figure 2. Winterkill on a golf course putting Ice Sheets green exacerbated by cross-country skiing.

Ice sheets may be identified as the cause of winterkill in turf. However, it is more often the cycle of crown hydration and refreezing that actually kills turf. This is an understandable mistake, since ice sheets may be created as snow melts and refreezes and they are very visible. Oftentimes, ice sheets will occur in low-lying or poorly drained areas where crown hydration may be facilitated because of the standing water. The damage closely aligns with the location of the ice Figure 3. Areas prone to collecting water may sheet, causing confusion as to the actual form ice sheets. cause of death (Fig. 3).

Recovery from Winterkill Low-Temperature Turfgrass Species Hardiness Confirmation of winterkill is necessary before going to the trouble and expense of Excellent Rough bluegrass reestablishment. If you suspect winterkill, take samples of the damaged area and place Creeping bentgrass them in a warm area to see if the turf greens Good Kentucky bluegrass up. Allow two weeks of recovery time before deciding on reestablishment practices. Colonial bentgrass

If reestablishment is indeed warranted, Medium Annual bluegrass seeding or sodding may be necessary to facilitate recovery. Well-defined areas of Tall fescue damage may be stripped of dead turf and re- sodded. Areas of more scattered damage Red fescue may be more easily reestablished by seeding. Poor Perennial ryegrass It will also be critical to divert traffic from newly seeded or sodded areas, and to provide light fertilizer applications to stimulate growth. -Adapted from Michigan State University’s Fact Appropriate irrigation during the Sheet Winterkill of Turfgrass (E0019TURF) by reestablishment period will also ensure that Dr. Kevin Frank the seedbed or sod stays moist.

Turfgrass Entomology 101

Insects are arguably the most successful life form specialized on plants that humans commonly on the planet in terms of diversity. Four out of grow. These species are considered pests—one every five organisms on Earth is an insect, and as type of insect herbivore that turfgrass is no individuals, they collectively outweigh every other stranger to. life form on the planet! Insects have been found in nearly every ecosystem, including glaciers and Turfgrass insect pests come in many shapes and even the ocean. Given this huge diversity and sizes—they can be beetles, bugs, or even moths ability to fill almost any habitat niche, it is not and flies. When we think of a beetle, we usually surprising that insects play a huge role in human think of the adult stage—a hard-bodied, six-legged life. In fact, turfgrass areas are home to many creature with a head, thorax, and abdomen types of insects—some are pests, but others are (Figure 4). However, it’s often the juvenile stages beneficial predators, and most are just minding of insects—commonly known as larvae, grubs, or their own business. caterpillars—that are pests in turf. These are the juvenile stages of insects with a complete Insects are animals in the phylum Arthropoda, metamorphosis life cycle (egg, larva, pupa, adult). meaning they have a hardened external skeleton In general, juvenile stages exist to feed and grow, and jointed appendages. Within Arthropoda, while adults exist to disperse and reproduce. Just insects are classified as hexapods, or as having six as human teenagers have seemingly bottomless legs. This classification differentiates insects from stomachs, juvenile insects have similarly voracious other arthropods, such as spiders (Arachnida), appetites. This is why the grub of a beetle or the which have eight legs, or millipedes and caterpillar of a moth is the stage we often think of centipedes (Myriapoda), which, as their name as a pest—because it is the stage that is feeding in indicates, have myriad (many) legs. order to continue development into adulthood.

It’s easy to dismiss insects as annoying or Some groups of insects go through gradual, or problematic when you are dealing with them incomplete, metamorphosis, where juveniles purely in a pest management context. Considering appear as smaller, wingless versions of adults and why insects are so often pests, being able to perform similar biological functions (except for distinguish damage caused by different pests, and reproduction). Often both adults and juveniles of being able to differentiate between pests and these insects may be considered pests. beneficial arthropods dwelling in turfgrass are all important steps to bringing a holistic and sustainable viewpoint to turfgrass management.

Why are insects so often pests?

The vast majority of insects are herbivorous, meaning they feed on plants. Some of these insects have evolved right along with plants we have grown for food and ornamentals. Not only are these plants highly nutritious by nature (otherwise, why would humans grow them?), but management practices like irrigation and fertilization make them even more so, and they are grown as monocultures over large areas of Figure 4. Diagram of typical beetle morphology, with fiddler land. This is a recipe for a feast for insect beetle as an example species, showing the head, thorax, and herbivores, and many species have become abdominal segmentation that is common to all insects. Turfgrass Entomology 101 (cont’d)

Common turf pests and their damage Turfgrass is grown widely in the Intermountain West, making the region an ideal locale for many insect herbivores that have evolved along with grasses that humans have cultivated for turf use. Common turfgrass insect pests in the region include billbugs (Figure 5), white grubs (Figure 6), sod webworms (Figure 7), and chinch bugs (Figure 8), each with their own unique biology (refer to figure captions for a physical description of the pest). Often, when the pest itself is hard to find, the damage it leaves behind can be a good identifier of its creator. Thus, it is important to know how to not only recognize the pest itself, but also its damage. Figure 6. A white grub is the larva of a beetle in the scarab family (Scarabaeidae). White grubs are c-shaped with three distinct pairs of legs. (Photo by David Cappaert, Michigan State University, bugwood.org).

White Grubs. The name “white grub” refers to the larvae of several species of beetle in the scarab family. Common scarab adults in turfgrass include Japanese beetles (Figure 11), May-June beetles, masked chafers, and black turfgrass ataenius. The larvae of these beetles damage turfgrass by chewing on the roots near the soil surface or just beneath the thatch layer, sometimes entirely severing roots. Early signs of damage include wilting and yellowing. In late summer when grubs are nearly fully developed, brown patches will begin to appear. Contrary to billbugs, white grubs Figure 5. Three species of billbug are commonly found in the do not feed on the crown of the turf, meaning that Intermountain West (clockwise from left): bluegrass billbug, hunting billbug, and Rocky Mountain billbug. Billbugs are a turf can survive damage even if the roots are type of beetle in the weevil family (Curculionidae). Adults have completely severed. Because of this, and because elbowed antennae, long snouts, and hard wing covers and they do not feed within stems, turf damaged by range in size from 6-12mm. white grubs does not pull away as easily as turf Billbugs. Billbugs are a type of beetle called a damaged by billbugs. Healthy turfgrass can mask weevil. Billbug damage is one of the most the presence of white grubs when infestations are commonly misdiagnosed problems in turfgrass light. (Figure 9). It is often mistaken for drought stress, Sod Webworms and Cutworms. In turf, most damage from other insect pests, delayed spring damage from sod webworms and cutworms is greening, or disease. Adults lay eggs in stems of seen on short-cut grasses of putting greens. New turfgrass, and larvae (Figure 10) emerge and sod fields and newly established lawns with high burrow down stems to the crown and roots of the fertility may also be preferred feeding sites for sod plant where they feed, resulting in patchy areas of webworms. Young sod webworm caterpillars chew dead grass. Billbug damage can be diagnosed on tender tissues of plant leaves and stems. using a simple “tug test”. Stems that have been Damage becomes evident when small, brown damaged by billbug feeding will pull away easily, and hollow stems will contain a saw dust-like material (frass, or insect feces). Turfgrass Entomology 101 (cont’d) patches of closely cropped grass appear, which can Beneficial turfgrass arthropods often be mistaken for disease. Cutworms are semi-subterranean pests that clip stems at the Not all insects inhabiting turfgrass are ground level, and damage appears as circular herbivorous. Many species feed on herbivores, spots of dead grass or depressed spots resembling helping to keep potentially damaging herbivore ball marks. These pests rarely cause problems in populations at levels where damage is reduced or high cut turf or home lawns, though it is possible. even unnoticeable. Some common predatory turfgrass insects include ground beetles (Figure 12), rove beetles (Figure 13), and ants. Wolf spiders are a non-insect arthropod predator abundant in Intermountain West turf. Other turfgrass arthropods perform different ecosystem roles, like decomposing organic matter. Spring- tails (Collembola) and pillbugs (AKA roly-polies, sowbugs, or woodlice are not arthropods but are terrestrial crustaceans) are two major groups of Figure 7. The life stages of a sod webworm, a moth pest of turfgrass in the family Crambidae. The caterpillars are the decomposers that may help manage turfgrass stage that feeds on and damages turf. (Photo by David Shetlar, thatch layers. Other decomposers in turf feed on The Ohio State University, bugwood.org). carrion, such as carrion beetles and burying beetles (Figure 14). Carrion beetles are often Chinch Bugs. Billbugs, white grubs, and found in turf near unmanaged, wooded areas webworms all go through complete where rodents and other vertebrates reside. metamorphosis, and the juveniles are considered the damaging life stage. Chinch bugs, on the other hand, have gradual As an informed turfgrass manager, it is important metamorphosis and several overlapping to know the difference between herbivorous generations throughout a season (Figure 8). species and beneficial insects you may find in your Both chinch bug nymphs and adults damage turf. Not all insect and arthropod activity means turfgrass by sucking sap from the crown. you should spray insecticides—some insects While feeding, they inject a salivary toxin that should be encouraged! There is no catch-all secret damages plant tissues and inhibits movement to telling if any given insect is an herbivore, predator, or decomposer except to become of water and nutrients throughout the plant. familiar with the turfgrass insects in this area. This initially results in a reddish-purplish discoloration of leaves, and advances to -Madeleine Dupuy, Utah State University, yellow, dry patchy areas as feeding continues. PhD Candidate Severe infestations can result in extreme thinning or even death of the turfgrass stand.

Figure 8. Hairy chinch bug life stages from nymphs to adult. Chinch bugs have incomplete metamorphosis, and both adults and nymphs from overlapping generations may damage turf simultaneously. Chinch bug juveniles—called nymphs—appear as smaller, wingless adults. Chinch bugs are “true bugs” (order Hemiptera) in the family Blissidae (Photo by David Shetlar, The Figure 9. Billbug damage at a golf course in Logan, UT (July Ohio State University, bugwood.org). 2013) very much resembles drought stress. Turfgrass Entomology 101 (cont’d)

Figure 10. Juvenile billbug life stages from egg (left) to pupa (right). Billbugs have 5 larval stages per generation that damage turf. Billbug larvae are legless and more robust than white grubs.

Figure 11. Two species of scarab—European chafer and Japanese beetle—whose larvae can be found damaging Intermountain West turf. Scarabs are a very diverse family whose members have a wide range of size and appearance. In turf, scarab adults may range in length from a couple of millimeters (black turfgrass ataenius) to a centimeter or more (masked chafers). (Photo by Bruce Watt, bugwood.org).

Figure 12. One type of predatory ground beetle you may commonly see in your lawn. Ground beetles are in the family Carabidae, a very diverse family whose members range in size from a couple of millimeters to a couple of centimeters. Ground beetles always have filiform antennae and a bean-shaped appendage—called a trochanter—where their hind legs meet the underside of their abdomen. Several species of ground beetle can be commonly found in turf. (Photo by Ken Chamberlain, The Ohio State University, bugwood.org).

Figure 14. A carrion-feeding burying beetle of the family Silphidae. Most carrion beetles you find in turf will have this general appeaance—the pointed abdomen extends slightly beyond the black and orange wing covers. Others you may find will appear disk-like with rumpled, black wing covers and a cream-colored thorax, often with a dark spot in the center. (Photo by Susan Ellis, USDA APHIS PPQ, bugwood.org).

Figure 13. Rove beetles are not your typical-looking beetle, but they are easily identified by their shortened wing covers that leave a good deal of their long, tapered abdomen hanging out. Rove beetles belong to the family Staphylinidae, another diverse family whose members broadly range in size and are commonly found in turf. Rove beetles can feed on both carrion and live prey. (Photo by Joseph Berger, bugwood.org). Upcoming Spring Management Practices

Seeding/Over-seeding Fertilization Aeration/Cultivation

Spring provides the Nitrogen is of primary Spring is also an ideal time opportunity to seed new concern in turfgrass to aerate your lawn if the turfgrass areas or to fertilization. In the soil is compacted or there over-seed areas that may spring, apply 1 pound of slow is a significant layer of have been damaged over the release nitrogen (N) fertilizer thatch beneath the grass. winter. The cool temperatures per one thousand square feet If the thatch underneath will promote germination and of lawn area. This will help your lawn is more than 1/2 growth of cool season turf the grass to recover from in. thick, consider core species such as Kentucky winter damage and any aeration to stimulate the bluegrass, tall and stress that may have natural decomposition fine fescues, and perennial occurred. It will also be process. Likewise, if you ryegrass. Be aware, that especially helpful for areas have a very fine-textured there will be also be annual that have suffered damage soil, compaction may weed pressure at this time of due to diseases such as pink occur, particularly in high year and consider your weed and gray snow mold. In a traffic areas. Core control options. Choose pest slow-release form, N fertilizer aeration will help to resistant or recommended will provide a alleviate compaction and will turfgrass cultivars when consistent source of nutrients encourage turfgrass growth possible. as the growing season and recovery. begins.

Relevant USU Fact Sheets

Basic Turfgrass Care Snow Mold in Turfgrass • Mowing, fertilization, and irrigation • Symptoms, diagnosis, and management

Turfgrass Cultivars for Utah Chinch Bugs • Appropriate species and varieties for Utah • Damage, diagnosis, and control options

Billbugs Sod Webworms • Damage, diagnosis, and control options • Damage, diagnosis, and control options

*Precautionary Statement: All pesticides have benefits and risks, however, following the label instructions will minimize the risk and maximize the benefit. Pay attention to the directions for use and follow precautionary statements. Pesticide labels are considered legal documents containing instructions and limitations. Inconsistent use of the product or disregarding the label is a violation of both federal and state laws. The pesticide applicator is legally responsible for proper use. Turfgrass IPM Advisory is published seasonally by Utah State University Extension.

Editor: Kelly Kopp, [email protected] click here http://utahpests.usu.edu/ipm/htm/advisories/turf for archived advisories. Utah State University is an affirmative action/equal opportunity institution.